Teachers' psychological wellbeing and school culture are important, but largely overlooked, factors in efforts to prevent adolescent problems and ensure young people's successful development. Burnout and depression are common among teachers. They affect the likelihood teachers will stay in the field and undermine teacher effectiveness. Teachers in schools that lack shared values, cooperation, and caring experience higher levels of burnout, which is a significant contributor to problems, including ineffective behavior management, high teacher turnover, low quality instruction, and coercive behavior. Yet, despite the importance of individual teacher's psychological wellbeing and a collegial school culture, research on strategies for improving these aspects of schools is seriously limited. One promising candidate for reducing teacher stress and creating effective school organizations consists of acceptance-focused interventions. This approach has led to a reduction in depression and burnout and stigmatizing attitudes toward clients of human service organizations. It has fostered adoption of evidence- based practices, and increased cooperation and support in preschools. To date no one has tested the value of this approach in public schools. We propose to conduct an experimental evaluation of an acceptance-focused intervention for reducing teacher distress and increasing school collegiality among middle school teachers. We intend to assign randomly 48 Oregon Middle schools, which are implementing Positive Behavior Support (PBS), to receive or not receive the intervention. We expect that teachers' psychological flexibility and wellbeing, school collegiality, use of positive behavior support practices, and the level of victimization among students will improve with the intervention. We will examine these outcomes in addition to results related to our secondary aim: an examination of whether the intervention has positive impact on more distal student outcomes of deviant peer formation, psychological wellbeing, behavioral outcomes, and academic performance. Potential moderators of intervention effects, such as pre-intervention levels of experiential avoidance, collegial relations, gender, school type and race/ethnicity of the staff will be examined. We will also test whether changes in response to the intervention mediate the association between the intervention condition and staff outcomes.